Distribution Of Radium Research Articles

Unique current connecting Southern and Indian Oceans identified from radium distributions

We examined the spatial variations in 226Ra and 228Ra (activities) concentrations from the surface to a depth of 830 m in the Indian and Southern Oceans from December 2019 to January 2020. 226Ra concentrations at the surface increased sharply from 30° S to 60° S along a ~ 55° E transect (1.4–2.9 mBq/L), exhibiting small vertical variations, while 228Ra decreased southward and became depleted in the Southern Ocean. These distributions indicated the ocean-scale northward lateral transport of 226Ra-rich and 228Ra-depleted currents originating from the Antarctic Circumpolar Current (ACC). 226Ra concentrations indicated that the fractions of the ACC at depths of 0–800 m decreased from 0.95 to 0.14 between 60° S and 30° S. The ACC fractions in the subantarctic western Indian Ocean were higher than those previously reported in the eastern Indian region, indicating preferential transport of the ACC. The fractions obtained were approximately equivalent to those in the western Indian Ocean in the 1970s. This could be attributed to the minimal southward shift of the polar front due to global warming over the last 50 years.

Dissolved Inorganic Carbon Transport in the Surface‐Mixed Layer of the Louisiana Shelf in Northern Gulf of Mexico

AbstractRivers and wetlands are a major source of terrestrial derived carbon for coastal ocean margins. This results in a net loss of terrestrial carbon into the shelf water and their subsequent transport to interior ocean basin. This study investigates the transport of dissolved inorganic carbon (DIC) in the surface‐mixed layer of Louisiana Shelf in northern Gulf of Mexico (nGOM) adjacent to the Wax Lake Delta (WLD) and Barataria Bay (BB), which represent contrasting net land gain and net land loss areas in this region. DIC samples were collected, in conjunction with short‐lived radium isotopes 224Ra (t1/2 = 3.66 days) and 223Ra (t1/2 = 11.43 days) samples during June and September 2019, to quantify shelf transport of DIC in the surface‐mixed layer during period of high and low river flow, respectively. Radium distribution implied shelf mixing rates of 140–6,759 and 63–2,724 m2 s−1 for WLD and BB regions, respectively, with more than tenfold decrease in rates between the two seasons. Net shelf transport of DIC was found to be highest for the WLD region in June, highlighting the importance of freshwater discharge in exporting DIC. An upscaling of our study for the entire Louisiana Shelf indicates that 1.54–20.19 × 109 mol C d−1 transported in June 2019 and 0.34–8.12 × 109 mol C d−1 in the form of DIC was exported across the shallow region of the shelf during high and low river flow seasons, representing an important source of DIC to the NGOM.

Radiation-ecological evaluation of rock dumps in the south zone of the Elkon uranium mine region (the Southern Yakutia)

This study aims at investigating the allocation conditions of rock dumps in the South zone located in the Elkon uranium mine region (the Southern Yakutia), and also at determining their radiation parameters as sources of technogenic contamination of the soil-vegetation cover and surface waters, and assessing the danger of these dumps for people. In this study, the generally accepted geographical methods were used, including comparative geographical and geochemical methods, as well as a combination of various radiometric research methods. The radiation parameters of the rock dumps of the South zone of the Elkon uranium mine region, the content and distribution of uranium, radium and radon in surface waters, as well as 238U content in technogenic soils at different distances from radioactive contamination sources were studied. It was found that the most active dumps, in terms of their radiation parameters, are located close to the radioactive ores, with the EDR of 1600-2150 R/h, effective specific activity - 20441-23640 Bq/kg, and uranium content of 1637-1888 mg/kg. The ranking of the studied dumps according to the degree of radiation hazard showed that 12 out of 31 dumps (39%) belong to the safe category, 6 (19%) belong to the category of potentially dangerous, and 5 and 8 (16% and 26%) were classified as dangerous and very dangerous respectively. In the conditions of the mountainous terrain, cold and humid climate of the studied area, these rock dumps, which are unevenly spread in mountain and taiga landscapes over the area of about 500 km2, are the main source of radioactive contamination of soil and vegetation cover and surface waters. The maximum contents of uranium, radium and radon in the studied surface waters were 18010-7 g/L, 4.710-12 g/L and 256.8 Bq/L respectively, which are 100, 8 and 198 times higher than their background concentrations in waters of natural landscapes. In the studied technogenic zones, a direct relationship was registered between the pollution intensity in surface water and that in the drained alluvial soils formed in the floodplains of these watercourses.

Mechanistic Modelling of Radium-223 Treatment of Bone Metastases

Despite the effectiveness of 223RaCl2 for treating castration resistant prostate patients with symptomatic bone metastatic disease, its mechanisms of action are still unclear. Even established dosimetric approaches differ considerably in their conclusions. With the rapid growth in the interest of alpha-targeted radionuclide approaches, in silico tumour models bring a new perspective to this as they can quantitatively simulate the interaction of αparticles with the predicted target(s). Here, we investigated three different mathematical models of tumour growth that take into account the radiation effect of Radium-223 treatments and compare the results to existing clinical data from the ALSYMPCA trial [1]. The well-established Gompertz growth model was applied to simulate metastatic tumour burden. Based on published measurements of Radium-223 uptake, we have incorporated the radiation effect of α-particles into the model and investigated three radium distribution scenarios - uniform exposure, exposure of only an outer layer, and exposure of a constant volume of the tumour. For each scenario, the times for various tumour stages to progress to the first symptomatic skeletal event were calculated. Uniform and outer-layer exposure scenarios showed very poor agreement with the KaplanMeier patient curves from clinical data. However, the constant volume effect predicted very similar outcomes to the observed clinical results, suggesting that only relatively small fractions of the cell population see damage from Radium-223. The commonly-used assumption of uniform Radium-223 distribution does not accurately reflect clinical responses. The suggestion that only a sub-population of the tumour might be affected by Radium-223 shows that there is a pressing need to further study the tumour and drug kinetics in order to schedule more effective treatments in the future. Given the clinical efficacy, even under these conditions additional preclinical studies are also required to test different radium distributions and their biological efficacy. This will ultimately aid in the design and implementation of future alpha-radionuclide targeted therapies. [1]Parker C, Nilsson S, Heinrich D, et al. Alpha emitter radium-223 and survival in metastatic prostate cancer. N Engl J Med. 2013;369:213-223.

Theoretical Assessment of the Effect of Vertical Dispersivity on Coastal Seawater Radium Distribution

Trends in radium activity in coastal seawater are frequently used to infer submarine groundwater discharge. In general, unlike in the deep oceans, radium samples are only collected from the surface of the mixed layer in coastal areas. The assumption is that the water column is well mixed, as often evidenced by uniform temperature and salinity profiles. However, if the timescale for vertical mixing is similar to or less than the timescale for radioactive decay, the vertical profiles in Ra activity may not be uniform. In the present work, a two-dimensional dispersion model was developed to evaluate the potential effects of slow vertical mixing on Ra distribution in the mixed layer of an inner shelf. The variables considered were the vertical coefficient of solute dispersivity (Kz), the offshore coefficient of solute dispersivity (Kx), the coastal Ra flux (Fo), the benthic Ra flux (FB) and the slope of the seabed. The shorter-lived Ra isotopes (223Ra and 224Ra; t1/2 = 3.66 and 11.4 days, respectively) were sensitive to Kz when its value was low (<10–4 m2 s–1), resulting in complex activity patterns in the water column as a function of the other variables. Radium-228 (t1/2 = 5.75 years) was only moderately impacted by low Kz but the long-lived 226Ra (t1/2 = 1600 years) was insensitive to Kz. Surface water samples may not always be representative of water column Ra activity when Kz is low, which will need to be taken into account in future field programs for seawater Ra distribution in shelf environments.

The radionuclide distribution onto different mineral phases of the rocks of the exocontact zone of Nizhnekansky granitoid massif

The sorption experiments with the five rock samples drilled in the deep-well in the exocontact zone of Nizhnekansky granitoid massif (EZNGM) in the range of depth 166–476m were carried out. The distribution of radium was studied. The radiograms of radionuclide sorption were obtained by digital autoradiography. Heterogeneous sorption of radium was demonstrated by digital radiography and phases with higher sorption ability were revealed. The technique for the treatment of radiograms with the help of ImageJ program for obtaining quantitative parameters of radionuclides distribution in the granite-gneiss rock samples was developed. Relative sorption efficiency of different mineral phases of the rock samples of Eniseysky area (EZNGM) toward radium is presented in the paper.

Radium isotopes distribution and submarine groundwater discharge in the Bohai Sea

In order to characterize the radium distribution and submarine groundwater discharge (SGD) in the Bohai Sea area, the three isotopes 223Ra, 224Ra and 228Ra in different water bodies were measured in a 4-year period with the radium-delayed coincidence counting (RaDeCC) system. The results indicated that radium activities take an order of groundwater > coastal seawater > river water > central seawater. The radium activities of groundwater were controlled by the lithology, human activities and salinity. Groundwater in aquifers with higher content of Th and U like igneous and metamorphic has higher radium activities, high salinity and oil exploitation which leads to groundwater contamination can also cause the higher radium activities. The radium isotopes of offshore waters were controlled by their respective onshore groundwater and SGD flux rates. The relative level of radium Ra isotope activity of coastal groundwater and nearshore seawater is determined by the interaction between groundwater and seawater. It is concluded that smaller radium mass transport from bottom sediments and the majority radium were supplied from landward groundwater from horizontal and vertical distribution of Ra isotope. The seasonal investigation showed that the seawater radium activities of 223Ra, 224Ra and 228Ra in autumn were higher than that in spring. Based on the seasonal variation of radium activities and the mass balance of radium, SGD of the Bohai Sea during rainy season were calculated to be 1.43 × 108 m3/d (3.73 × 10−3 m3/m2/d) in northern region and 2.84 × 107 (1.76 × 10−3 m3/m2/d) in western region by 228Ra.

Carbon outwelling across the shelf following a massive mangrove dieback in Australia: Insights from radium isotopes

Abstract Mangrove soil carbon stocks are known to decrease following forest loss due to respiration and enhanced soil CO2 emissions. However, changes in carbon outwelling to the coastal ocean due to mangrove forest disturbance have not been considered. In December 2015, an extremely large mangrove dieback event (∼7000 hectares, spanning 1000 km of coastline) occurred in the Gulf of Carpentaria, Australia. To assess the effect this dieback event had on carbon outwelling, we used radium isotopes and dissolved carbon measurements (dissolved organic carbon, DOC, dissolved inorganic carbon, DIC, and total alkalinity, TAlk) to estimate cross-shelf carbon transport from living and dead mangrove areas and to calculate the carbon losses from living and dead forest soils via SGD. Radium distributions imply cross shelf eddy diffusivity of 107.5 ± 26.9 and 104.6 ± 23.9 m−2 s−1 from dead and living areas and radium water ages reveal that mangrove carbon reaches 10 km offshore within 7 days. Outwelling rates from living and dead areas were explained by soil carbon losses via SGD. This study suggests a decrease in carbon outwelling to the ocean from dead forest areas compares to living areas by 0–12% for DOC, 50–52% for DIC and by 37–51% for TAlk ∼8 months after the dieback event occurred. Changes to oceanic carbon outwelling rates following mangrove loss are likely driven by a gradual depletion of carbon stocks from the sediment profile.

Role of Trace Elements in the 226-Radium Incorporation in Sulfate Minerals (Gypsum and Celestite)

Incorporation of 226Ra within gypsum (CaSO4·2H2O(s)) and celestite (SrSO4(s)) was assessed through dedicated batch experiments monitored over hundreds of days. Dissolution/recrystallization and coprecipitation experiments were carried out to investigate a range of chemical conditions, close to or far from equilibrium conditions. These data were used to establish the ability of gypsum and celestite to incorporate 226Ra. Celestite shows a high 226Ra incorporation, with a partition coefficient around 105. On the contrary, 226Ra is not significantly incorporated into pure gypsum. A very low value of (8.8 ± 1.5) × 10–4 has been estimated, which is much lower than the values reported in the literature. This may explain why 226Ra incorporation in gypsum is enhanced when Sr impurities are present (above 0.1 molar %). Under such conditions, the radium distribution coefficient is around 0.15 ± 0.09. This behavior can be explained by an ion-exchange mechanism between 226Ra and Sr, consistently with the existence of ...

Mechanistic Modeling of Radium-223 Treatment of Bone Metastases

Despite the effectiveness of 223RaCl2 for treating patients with symptomatic bone metastatic disease, its mechanisms of action are still unclear. Even established dosimetric approaches differ considerably in their conclusions. In silico tumor models bring a new perspective to this situation because they can quantitatively simulate the interaction of α-particles with the target(s). Here, we investigated 3 different mathematical models of tumor growth that consider the radiation effect of radium-223 (223Ra) treatments and compared the results with clinical data. The well-established Gompertz growth model was applied to simulate metastatic tumor burden. On the basis of published measurements of 223Ra uptake, we have incorporated the radiation effect of α-particles into the model and investigated 3 radium distribution scenarios-uniform exposure, exposure of only an outer layer, and exposure of a constant volume of the tumor. For each scenario, the times for various tumor stages to progress to the first symptomatic skeletal event were calculated. Uniform and outer-layer exposure scenarios showed very poor agreement with the Kaplan-Meier patient curves from clinical data. However, the constant-volume effect predicted outcomes very similar to the observed clinical results, suggesting, depending on the dose rate, that relatively small fractions of the cell population see damage from 223Ra. The commonly used assumption of uniform 223Ra distribution does not accurately reflect clinical responses. The suggestion that only a subpopulation of the tumor might be affected by 223Ra shows a pressing need to further study the tumor and drug kinetics to schedule more effective treatments in the future.

Human exposure to radon radiation geohazard in Rong Cave, Dong Van Karst Plateau Geopark, Vietnam

Human exposure to radon radiation geohazard in Rong Cave, Dong Van Karst Plateau Geopark, Vietnam

Detailed effects of particle size and surface area on 222Rn emanation of a phosphate rock

The dependency of radon emanation on soil texture was investigated using the closed chamber method. Ground phosphate rock with a large specific surface area was analyzed, and the presence of inner pores, as well as a high degree of roughness and heterogeneity in the phosphate particles, was found. The average radon emanation of the dry phosphate was 0.145 ± 0.016. The emanation coefficient was highest (0.169 ± 0.019) for the smallest particles (<25 μm), decreasing to a constant value (0.091 ± 0.014) for the larger particles (>210 μm). The reduction rate followed an inverse power law. As expected, a linear dependence between the emanation coefficient and the specific surface area was found, being lower than predicted for the large specific surface area. This was most likely due to an increase in the embedding effect of radon atoms in adjacent grains separated by micropores. Results indicate that knowledge of grain radium distribution is crucial to making accurate emanation predictions.

Radon exhalation from granite countertops and expected indoor radon levels

Radon (222Rn) exhalation rates from granite countertops were measured using a continuous radon monitor. The countertops could be separated in three groups according to radon their exhalation rates. However, even for a worst-case scenario (e.g. E ~ 1.10 Bq m−2 h−1, no air circulation and full tile home) the contribution to indoor radon concentration is estimated to be [Rn] < 100 Bq m−3. In addition, despite the uneven radium distribution in the granite slabs, there is significant correlation (r 2 = 0.50) between the measured radon levels and the radium content of the granites.

RADON MIGRATION IN SOIL AND ITS RELATION TO TERRESTRIAL GAMMA RADIATION IN DIFFERENT LOCATIONS OF THE GREEK EARLY WARNING SYSTEM NETWORK

Radon concentration as function of the soil depth was measured during the years (2011-2015), in a location of the Aristotle University campus. Radium distribution in soil was found constant. On the contrary, as expected, radon concentration increases with soil depth. The experimental distribution was reproduced by solving the general transport equation (diffusion and advection). From the general radon migration (diffusion and advection) equation it was indirectly deduced, from the measured radon profile in the soil, the radon exhalation rate from the soil (26.7±4.5 Bq m-2 h-1). In the same location, during 2010-2015, 113 direct radon exhalation measurements were performed and give an average value for the 6 years of 21.1±3 Bq m-2 h-1. The comparison between the radon exhalation rates deduced by the indirect and direct method indicates the validity of the diffusion advection model predictions concerning the radon exhalation rate from soil. The relation between radon migration in soil and terrestrial gamma radiation was studied. In particular, in the present study was investigated the correlation between gamma radiation 1 m above soil and radon exhalation in six locations of the Greek early warning system network. A positive correlation between gamma dose rate in air and radon exhalation rate from soil was found.

FRACTAL AND CHAOS ANALYSIS FOR DYNAMICS OF RADON EXHALATION FROM URANIUM MILL TAILINGS

Tailings from mining and milling of uranium ores potentially are large volumes of low-level radioactive materials. A typical environmental problem associated with uranium tailings is radon exhalation, which can significantly pose risks to environment and human health. In order to reduce these risks, it is essential to study the dynamical nature and underlying mechanism of radon exhalation from uranium mill tailings. This motivates the conduction of this study, which is based on the fractal and chaotic methods (e.g. calculating the Hurst exponent, Lyapunov exponent and correlation dimension) and laboratory experiments of the radon exhalation rates. The experimental results show that the radon exhalation rate from uranium mill tailings is highly oscillated. In addition, the nonlinear analyses of the time series of radon exhalation rate demonstrate the following points: (1) the value of Hurst exponent much larger than 0.5 indicates non-random behavior of the radon time series; (2) the positive Lyapunov exponent and non-integer correlation dimension of the time series imply that the radon exhalation from uranium tailings is a chaotic dynamical process; (3) the required minimum number of variables should be five to describe the time evolution of radon exhalation. Therefore, it can be concluded that the internal factors, including heterogeneous distribution of radium, and randomness of radium decay, as well as the fractal characteristics of the tailings, can result in the chaotic evolution of radon exhalation from the tailings.

Radium distribution in anthropogenic soils as a function of soil physicochemical and mineralogical parameters

We investigated the effects of physicochemical and mineralogical compositions of radioactively contaminated podzolic and soddy–meadow soils on the 226Ra distribution in the soil profile. It was shown that the physicochemical compositions of soils depend on the type of contamination and have different effects on the mobility of the radionuclide. The presence of phosphorus and organic matter was shown to reduce 226Ra mobility. The highest Ra content was observed in the fraction <10 µm. The role of the composition of the fine fraction of the anthropogenic soil was evaluated. Relations between 226Ra and organic matter contents in different size fractions are satisfactorily described by the logarithmic function CRa = a + bln(Corg) (R2 = 0.9, p < 0.05). The concentrations of 226Ra and organic matter show a positive correlation with relative percentages of illite- and smectite-group minerals and a negative correlation with chlorites.

Factors influencing the distribution of 223Ra and 224Ra in the coastal waters off Tanggu and Qikou in Bohai bay

The naturally occurring 223Ra and 224Ra isotopes have become an established tool for investigating water mixing and submarine groundwater discharge (SGD). In this paper, we used the radium delayed coincidence counter (RaDeCC) to measure 223Ra and 224Ra activities, the distributions of 223Ra and 224Ra in two coastal waters with different hydrographical conditions and its influence factors were explored in Bohai bay. The results indicated that the Ra concentration was constrained by coastal land use patterns, the type of water and the geochemical environment. The Ra concentrations in groundwater and beach water were generally higher than the Ra concentrations in offshore waters. In the highly urbanized and industrialized Tanggu area, both of 223Ra in coastal water (average 3.74dpm/100L) and 224Ra (average 41.3dpm/100L) were lower than that in the undeveloped Qikou area (average 9.65dpm/100L and 148.9dpm/100L for 223Ra and 224Ra, respectively). Urbanization and Marine reclamations have modified local hydrogeological conditions, and then reduced SGD fluxes. Human activities have poured much more contaminants into coastal oceans and changed local aqueous environments, thus resulted all chemical compositions were richer in the urbanized coastal waters. With respect to the relationships between radium and the chemical compositions of the waters, radium was negatively related to salinity, nitrate and sulfate but was positively related to the concentration of cations such as calcium and magnesium. The apparent residence ages and SGD fluxes were also estimated from the radium distributions. There were more SGD fluxes into the coastal water off Qikou (9.88×107 m3/d) than into the water off Tanggu (1.22×107 m3/d).

Inappropriate attempts to use distributions of 228Ra and 226Ra in coastal waters to model mixing and advection rates

Numerous investigators have used the advection–diffusion equation and the distributions of the four isotopes of radium to model coastal mixing rates. However, there is a dichotomy in approach. Some models use the short-lived 224Ra (T1/2=3.7 days) and 223Ra (T1/2=11 days) to determine horizontal mixing coefficients and the long-lived 226Ra (T1/2=1600 years) and 228Ra (T1/2=5.75 years) to test for the effects of advection. Because the timescales of mixing in most coastal systems (10–80km offshore) are on the order of months or less, radioactive decay and particle removal of the long-lived isotopes are neglected in these models. If the long-lived isotopes display a linear gradient with distance offshore, this is taken as evidence that conservative mixing rather than advection controls the radium distribution. In this case it is appropriate to neglect the advection term and calculate mixing rates based on the exponential decay of the short-lived isotopes. Other models assume that radioactive decay of all of the isotopes impacts their distribution offshore. These models set up equations that separate the effects of mixing from advection and attempt to force mixing rates derived from all of the Ra isotopes to match. There are several reasons these models are doomed to fail. First, 224Ra and 223Ra look at different scales of mixing-there is no reason they must give the same rate. Secondly, on the timescale of coastal mixing decay of 226Ra and 228Ra is essentially zero. Equations that include decay terms for 226Ra and 228Ra become unrealistic when we consider that the measurement error is considerably greater than decay. In fact particle removal of 226Ra is more important than radioactive decay. Finally, these models require steady-state conditions on the timescales of the decay terms. In order to use such models, the source functions and distributions of 228Ra and 226Ra would have to be constant for several times their half lives, approximately 25 and 4000 years, respectively. Seasonal and annual variability in supply and mixing rearranges the distributions, violating the steady-state assumption. Thus, models utilizing 226Ra and 228Ra radioactive decay are useless in the coastal zone.

Investigation of some factors affecting on release of radon-222 from phosphogypsum waste associated with phosphate ore processing

The aim of this study is oriented to investigate the influence of some physicochemical factors such as radium distribution, grain size, moisture content and chemical constituents on releases of radon-222 from the accumulated phosphogypsum (PG) waste. The emanation fraction, activity concentration in the pore and the surface exhalation rate of radon-222 in the bulk PG waste are 34.5 ± 0.3%, 238.6 ± 7.8 kBq m−3 and 213 ± 6.9 mBq m−2 s−1, respectively. These values were varied and enhanced slightly in the fine grain sizes (F1 < 0.125 mm) by a factor of 1.05 folds compared to the bulk residue. It was also found that release of radon from residue PG waste was controlled positively by radium (Ra-226), calcium (CaSO4) and strontium (SrO). About 67% of radon release attributed to the grain size below 0.5 mm, while 33% due to the large grain size above 0.5 mm. The emanation fraction of Rn-222 is increased with moisture content and the maximum emanation is ∼43% of moisture of 3–8%. It reduced slowly with the continuous increase in moisture till 20%. Due to PG waste in situ can be enhancing the background to the surround workers and/or public. Therefore, the environmental negative impacts due to release of Rn-222 can be minimized by legislation to restrict its civil uses, or increasing its moisture to ∼10%, or by the particle size separation of the fine fraction containing the high levels of Ra-226 followed by a suitable chemical treatment or disposal; whereas the low release amount can be diluted and used in cement industry, roads or dam construction.

Submarine groundwater discharge and nutrient addition to the coastal zone of the Godavari estuary

Submarine groundwater discharge (SGD) represents a significant pathway of materials between land and sea, especially as it supplies nutrients, carbon and trace metals to coastal waters. To estimate SGD fluxes to the Godavari estuary, India, we used multiple tracers: salinity, Si, 223Ra, 224Ra, 228Ra and 226Ra. Tracer abundances were elevated in groundwater from the unconfined coastal aquifer and in surface water from the near shore zone; these enrichments decreased to low levels offshore, indicative of groundwater discharge. A model based on the decay of 224Ra relative to 228Ra was used to determine apparent water ages of various bays within the estuary. These ages ranged from 2.6 to 4.8d during November 2011. Knowing the water age, the distribution of radium in the estuary, and the radium isotopic composition of groundwater enabled us to calculate SGD fluxes to the estuary. These fluxes (in units of 106m3d−1) were on the order of 5 in the Gautami Godavari estuary, 20–43 in the Vasishta Godavari estuary, and about 300 in Kakinada bay, where enhanced ion exchange processes and redox-controlled cycling in the mangrove ecosystem may contribute to higher fluxes. These estimates of water fluxes allowed us to determine the magnitude and seasonal variability in the nutrient fluxes to the estuary associated with SGD. These nutrient fluxes (in units of mmolm−2d−1) ranged from 1–19 (N), 0.6–2.6 (P), and 5–40 (Si) in Gautami Godavari; 19–40 (N), 2.6–5.5 (P), and 200 (Si) in Vasishta Godavari; and 120–140 (N), 10 (P), and 220 (Si) in Kakinada bay. The high SGD fluxes to Kakinada bay contribute significant nutrients to this bay; considerably lower SGD fluxes to Vasishta Godavari still contribute significant nutrients to this estuary. Thus SGD represents a major source of new nutrients to these coastal ecosystems. For the entire Godavari estuarine system, SGD fluxes contribute (48–88)×109molDICy−1 and (51–94)×109molTAy−1. These fluxes represent ~54 and ~62% of the riverine DIC and TA fluxes to the Godavari estuarine system. This study provides baseline data against which future changes in nutrient and carbon fluxes due to urbanization and economic growth over this region can be compared.